410 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



[November, 



the contrar)-, extend when the action flags. The jiarts necessary to eftect 

 these different changes connect tlie valves with axes moved by the engine, by 

 means of a contrivance of which Watt conceived the idea from the regulator 

 employed in some of the flour mills. He called it the governor, it is also 

 termed the centrifugal power regulator. Its efficiency is such that some 

 years ago there was, in the cotton-mill of Mr. Lee, a mechanic of great 

 talent, a clock set in motion by the steam-engine of the factory, and wliich 

 acted almost as well as the ordinary spring clock by its side.— .see fiq. 15. 



M'att's governor is the secret, the principal secret, of the astonishing per- 

 fection of the manufacturing products of the age ; it is that which gives the 

 steam-engine an action free from any vibration, and which enables it with 

 equal success to embroider muslin and to forge anchors ; to weave the most 

 delicate fabrics, and to communicate rapid motion to the massive stones 

 of the flour mill. This explains why Watt said, without being liable to the 



Fig. 13 & 14. 



tkj^ 



PARALLEL MOTION. 



The apparatus adopted for carrying this motion into effect, is represented in 

 fig. 13, wliich is an elevation, or side view of one half of the engine beam ; 

 and fig. 14, a plan of same ; similarletters, in both figures, refer to similar parts; 

 the beam moving on its axis A, every point in its arm moves in the arc af a 

 circle, of which A is the centre. Let B be the point which divides the arm, 

 A F into equal parts A B, and B F, and let D C be a straight rod, equal in length 

 to A B, and playing on the fixed centre or pivot C. The end D of this rod, is 

 connected by a straight bar D B, with the point B, by pivot at B and D, on 

 which the rod B D plays freely. If the beam be supposed to move alter- 

 nately on its axis A, the point B will move up and down in a circular arc, of 

 which A is the centre, and at the same time, the point E will move in an 

 equal circular arc round the point C as a centre, therefore, the middle point 

 K of the rod B D will move up and down in a straight line. 



Also let a rod P G equal in length to B D, be attached to the end/ of the 

 beam by a pivot, on which it moves freely, and let its extremity G be con- 

 nected with L, by a rod G D, equal in length to B F, and playing on pivots, 

 G and D. 



By this arrangement, the joint F G being always parallel to B D. the three 

 points A F G wdl be, in circumstances, precisely similar to the points, ABE, 

 except that the system A F G will be on a scale of double the magnitude of, 

 ABC; A F being twice A B, and E G twice B E, it is clear, then.'^that what- 

 ever course the point E may follow, the point G must follow a smiilar line, but 

 will move twice as fast. But, since the point E has been already shown to 

 move up and down in a straight line, the point G must also move up and down 

 in a straight line, but of double the length. 



By this arrangement, the pistons of both the steam cylinder and air pump 

 are worked ; the rod of ihe latter being attached to the point E, and that of 

 the former, to the point G. 



Fig. 15. 



THE GOVERNOR. 



Different modes of combining the parts are used 

 by different engineers; one of these is shown in figure 

 15, where g is the revolving axis, /the point of sus- 

 pension, j j the balls, e e the rods by which the 

 balls are suspended. These rods are connected to the 

 rods i I, and by that means raise or depress the 

 sliding piece A, and with it the lever I, which acts on 

 the throttle valve, by the line C. The parts marked 

 k k are two rests to receive the balls when the engine 

 is cot in motion. 



imputation of exaggeration, that to avoid the runnings in and out of senants, 

 in case of illness, he would have his medicine given to him by arms from his 

 steam-engine. I know very well, that with the common run of the world, 

 this ease of action is supposed to be obtained at the expense of the power 

 employed, but it is a vulgar error; the saying "great noise and little work," 

 is not only true in the moral world, but is a mechanical axiom. 



A few words more, and we shall get to the end of the technical details. 

 Some years ago great benefit was found from not leaving a free communi- 

 cation between the boiler and the cylinder, during the whole duration of each 

 stroke of the engine. This communication was shut off when the piston, for 

 instance, had made one third of its stroke ; the two remaining thirds of the 

 length of the cylinder were then gone through, in consequence of the speed 

 acquired, and particularly on account of the expansion of the steam. Watt 

 had already pointed out this process,* and very good judges place this im- 

 provement, on account of its practical application, on a par with the con- 

 denser. It is very certain, that since its adoption, the Cornish engines have 

 produced unexpected effects, and that, with one bushel of coals, they do the 

 work of twenty men working for ten hours. We must recollect that, in the 

 coal districts, a bushel of coals costs only nine pence, and then we sliall see 

 clearly that Watt reduced, in the greater part of England, the price of a 

 man's days' labour of ten hours to less than a halfpenny! f 



Numerical calculations show so clearly the value of the inventions of our 

 colleague, that I cannot refrain from showing two other comparisons, wliich 

 I have borrowed from one of the most celebrated correspondents of the 

 Academy, Sir John Herschel. 



The ascent of Mont Blanc, from the valley of Chamouni, is justly con- 

 sidered as one of the most laborious tasks which a man can get through in 

 two days. Thus the maximum of mechanical exertion of which we are ca- 

 pable in twice twenty-four hours, is measured by raising the weight of our 

 body to the height of Mont Blanc. This labour, or the equivalent of it, a 

 steam-engine will effect by burning two pounds of coal. Watt has therefore 

 shown, that the daily strength of a man does not exceed that which is con- 

 tained in a pound of coal. 



Herodotus relates that the construction of the gi'eat pvTamid of Egypt oc- 

 cupied a hundred thousand men twenty years. The pjTamid is of limestone; 

 its volume can be easily calculated, and is ascertained to be about tlurteen 

 millions of pounds. To raise this weight 125 feet, the height of the centre 

 of gravity of the pyramid, it would be necessary to burn, under the boiler of 

 a steam-engine, 630 chaldrons of coal. There is, among our neighbours, a 

 foundry which could be mentioned, which burns a greater quantity of fue 

 eveiy week. 



Copying Machine — Heating by Steam — Composition or Water — 

 Bleaching by Chlorine — Experiments on the Physiological 

 Effects of breathing Different Gases. 



Birmingham, when Watt took up his residence there, reckoned, among 

 the inhabitants of its neighbourhood, Priestley, whose mere name speaks 

 everything, Darwin, author of the Zoonomia, and of a celebrated poem on 

 " The loves of the plants," Withering, a distingiushed physician and botanist, 

 Keir, a chemist well known by his notes on the translation of Macquer, and 

 an interesting memoir on the crystallization of glass, Galton, who wrote an 

 elementary treatise on Ornitholog)', Edgeworth, author of several works justly 

 appreciated, and father of the so celebrated Miss Maria, &c. These savanst 

 soon became intimate with the celebrated mechanic, and most of them fonned, 

 in conjunction with him and Boulton, a club, under the name of The Lunar 

 Society. Such a singular title gave rise to many strange mistakes, although 

 it only meant that they met on the evening of the fuU moon, a time of the 

 month chosen in order that the members might see their way home on 

 lea%ing. 



Every meeting of the Lunar Society fuinished Watt with a fresh oppor- 

 tunity of showing the incomparable fertility of imagination with wliich nature 



* The principle of cutting otf the steam. Watt had already clearly shown in a letter 

 to Dr. Small, (lateii I7G9, and it was put in practice at Suho in 1776, and in 1778 at 

 the Sliadwell Water Works on economic grounds. The mvenlion and the advantaj;es to 

 be derived from it are fully described in the patent of 1782.— iVofe of M. Arago. 



t At a time when so many persons are employed iu planning rotatory engines, 1 

 should be unpardonably forgetful if 1 did not mention that Watt not only turned his at- 

 tention to this subject, as we see in his patents, but that he carried it into execution. 

 These engines Watt gave up, not because they would not act, but because they seemed 

 to him in a working point of view very much inferior to the double impulse and recti- 

 linear action engines. 



There are few inventions great or small, among those which have been contributed to 

 the modern steam engine, which were not first developed by Watt. Follow liis labours, 

 and we shall find that besides the principal points enumerated minutely in the test, that 

 he pioposed tliat in places where there was a deficient supply of cold water, engines 

 without condensation, that is to say, engines in wliich the steam after having acted is 

 discharged into the atmosphere. Expansive steam for engines with several cylirrlers, 

 was also among Watt's plans, and he suggested the idea of pistons perfectly closed, al- 

 though composed of pieces of metal. It was also Watt who suggested the use of the 

 niercurial guage to show the elasticity of the steam in the boiler and in the cund' n-er ; 

 who pointed out a simple and permanent guage,* by means of which the quaiiiity of 

 water in the boiler always can be told at once ; who to prevent the quantity of water 

 being diminished to a dangerous extent, combined the movements of the feeding pump 

 to those of a float ; who attached to au opening on the covering of the principal cylinder 

 of the engine an indicator, combined in such a way as to shew exactly the law of eva- 

 cuation of the steam in relation with the positions of the piston, &c., &c. If 1 had time 

 I would shew that Watt was not less skilful and successful in his attempts to improve 



the boiler, to diminish the loss of heat, and to burn completely the quantity of s ke 



which issued from the ordinary chimneys, how high soever tUey may be. — Aofe of M. 

 Araifo. 



• Stuart attributes this to Smeaton.— J\'o(e of Translator. 



